The recent shift in the consumer electronics industry from an emphasis on analog technology to a preference for digital technology is largely based on the fact that the former generally limits the user to a role of a passive recipient of information, while the latter is interactive and allows the user to control what, when and how he or she receives and manipulates certain information. This shift in focus has resulted in the development and increasingly widespread use of a digital device generically referred to as a "personal digital assistant" (PDA). PDAs are wireless, hand-held electronic devices that may be connected to a desktop personal computer (PC) or other PDAs via an infrared link. Unlike PCs, which are general purpose devices geared toward refining and processing information, PDAs are designed to capture, store and display information originating from various sources. Additionally, while a certain level of skill and experience is required to use a PC effectively, PDAs are designed with the novice and non-computer user in mind.
PDAs are often described as an electronic alternative to the filofax; however, devices such as electronic books, electronic note takers, personal computers, display telephones and personal communicators may also be embodied as PDAs. Regardless of their embodiment or specialized functions, PDAs' primary functions are to capture and store information, search the stored information efficiently, access and display the results of the search, update the information and reconcile the information with data stored on a PC.
Clearly, the trade off for decreased size and increased portability is a decrease in the capabilities that can be built into a PDA. For example, PDAs have a very small display area that typically is much smaller than the stored document being viewed by the user. It is therefore necessary for PDAs to be equipped with a convenient scrolling mechanism, so that the user is able to view the entire document by scrolling the display up and down or side to side. Most PDAs are equipped with cursor keys for this purpose, with a user being required to press the appropriate key(s) to scroll the screen in the desired direction until the desired portion of the document is displayed on the screen. Alternatively, scroll bars, which are common features of most of the graphical user interfaces (GUIs) available for use on PCs, may be used to manipulate and scroll the display.
One problem with the above scrolling techniques is that, in some implementations, they may be counterintuitive, i.e., the movement of the cursor keys or the scroll bars does not intuitively correspond to the resulting movement of the display. Another problem is that the above techniques enable scrolling in only the X and Y directions, which makes moving about in a large document more difficult and time consuming than would be the case if nonrectilinear scrolling were supported. For example, assuming the document is organized in colurines, similar to a newspaper, a user will likely find it more convenient, as well as more intuitive, to scroll directly to the top of the next column than to scroll over to the next column and then up to the top of the column, or vice versa.
Therefore, what is needed is a scrolling mechanism for use with a PDA which is completely intuitive and which enables a user to scroll in nonrectilinear directions.